A new study has revealed that the way fruit bats use biosonar to ‘see’ their surroundings is significantly more advanced than first thought.
The study examines Egyptian fruit bats (Rousettus aegyptiacus), which use echolocation to orient inside their caves and to find fruit hidden in the branches of trees.
Their high-frequency clicks form a sonar beam that spreads across a fan-shaped area, and the returning echoes allow them to locate and identify objects in that region.
As these bats were considered to have little control over their vocalizations, scientists have puzzled over how they are able to navigate through complex environments.
The research team, led by Nachum Ulanovsky of the Weizmann Institute in Israel and Cynthia Moss of the University of Maryland, reports that these bats adapt to environmental complexity using two tactics.
First, they alter the width of their sonar beam, similar to the way humans can adjust their spotlight of attention in order to spot, for example, a friend in a crowded room. Second, they modify the intensity of their emissions.
“The work presented here reveals a new parameter under adaptive control in bat echolocation,” said Ulanovsky.
“This is the first report, in any sensory system, of an active increase in field-of-view in response to changes in environmental complexity,” he stated.
Although these new findings may be unique to Egyptian fruit bats because of their rapid tongue movements, Ulanovsky explained that their results “suggest that active sensing of space by animals can be much more sophisticated than previously thought – and they call for a re-examination of current theories of spatial orientation and perception.”
The study was published September 13 in the online, open access journal PLoS Biology.